JP6629638B2 - Non woven sheet - Google Patents

Description

  The present invention relates to a nonwoven fabric sheet that can be suitably used for wipers and the like.

In recent years, nonwoven fabrics composed of so-called nanofibers having a fiber diameter of 1 μm or less have been studied because they have many fine voids and high air permeability (Patent Document 1).
On the other hand, the applicants of the present application have developed a sanitary tissue paper containing, as one kind of nanofibers, metal-supported cellulose fibers in which metal particles are supported on oxidized cellulose fibers (TEMPO oxidized cellulose fibers) (Patent Document 2).

JP 2012-550 JP 2015-45113 A

By the way, the nonwoven fabric described in Patent Document 1 is manufactured by a wet papermaking method by mixing nanofibers with other fibers or the like. There is a problem that liquid retention is low.
Further, in recent years, it has been required to impart a deodorant and antibacterial function to a nonwoven fabric sheet.
Accordingly, an object of the present invention is to provide a nonwoven fabric sheet having a sufficient deodorizing antibacterial function and excellent strength.

In order to solve the above problems, the nonwoven fabric sheet of the present invention is characterized in that Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, and the like are used for oxidized cellulose fibers having a carboxyl group or a carboxylate group on the surface. Bonding of metal ion-containing cellulose fibers containing ions of one or more metal elements selected from the group of Cu and synthetic fibers that are one or more fibers selected from the group of polyethylene, polypropylene and polyethylene terephthalate Do it.

Preferably includes a pre-Symbol metal ion-containing cellulose fibers 2 to 30 mass%.
It is preferable that the content of the metal ion to the nonwoven fabric sheet is a 60~510mg / ^{m 2.}

  ADVANTAGE OF THE INVENTION According to this invention, while having sufficient deodorant antibacterial function, the nonwoven fabric sheet excellent in intensity | strength is obtained.

It is a figure which shows the transmission electron microscope image of the metal ion containing cellulose fiber used for the Example.

The nonwoven fabric sheet according to the embodiment of the present invention is formed by bonding metal ion-containing cellulose fibers described below and synthetic fibers. The phrase “both fibers” are “bonded” means that both fibers cross and contact with each other on a transmission electron microscope image of the nonwoven fabric sheet.
Synthetic fibers improve the strength of the nonwoven sheet and increase the paper strength against wet and chemical resistance. Examples of the synthetic fibers include one or more fibers selected from the group consisting of polyethylene, polypropylene, and polyethylene terephthalate.

As a method for bonding the metal ion-containing cellulose fiber and the synthetic fiber, a first web containing the metal ion-containing cellulose fiber and an original nonwoven fabric sheet of the synthetic fiber manufactured by a spun bond method and / or a melt blown method are mixed with a water stream. It can be manufactured by conjugation.
Alternatively, it can be produced by placing a metal ion-containing cellulose fiber on an original nonwoven fabric sheet of synthetic fiber produced by a spunbond method or a melt blown method, and binding them by hydroentanglement.
As described above, the strength is improved by manufacturing the nonwoven fabric sheet based on the original nonwoven fabric sheet of synthetic fibers in which the fibers are tightly entangled.

The first web containing the metal ion-containing cellulose fiber can be produced by a wet papermaking method after preparing a stock by mixing the metal ion-containing cellulose fiber with other fibers as necessary. Examples of other fibers include pulp fibers such as N-BKP, rayon fibers, and heat fusion fibers.
Further, the first web may be manufactured by a dry air laid method or a card method. In this case, fibers obtained by opening the raw material sheet with a hammer mill or the like can be used.
Further, if the web contains heat-fused fibers, the bonding force between the fibers increases in the drying step, and higher strength can be obtained.
The first web is then bonded to the original nonwoven sheet by a hydroentanglement method. At this time, in order to prevent the fibers from falling off from the first web, the fiber length of the fibers constituting the first web is adjusted. 1.5 mm or more is desirable.

The nonwoven fabric sheet preferably contains 2 to 30% by mass of the metal ion-containing cellulose fiber.
If the ratio of the metal ion-containing cellulose fiber in the base paper is less than 2% by mass, the antibacterial deodorizing function is reduced, and if the ratio of the metal ion-containing cellulose fiber exceeds 30% by mass, the cost may be increased.

The basis weight of the nonwoven fabric sheet can be, for example, 20 to 200 g / m ² .
Further, the thickness of the nonwoven fabric sheet can be set to 0.2 to 2.0 μm (measured according to JIS-P8118).
The strength of the nonwoven fabric sheet can be 1000 to 6000 gf / 25 mm.

The metal ion-containing cellulose fiber is selected from the group consisting of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn and Cu with respect to the oxidized cellulose fiber having a carboxyl group or a carboxylate group on the surface. It contains ions of more than one kind of metal element.
Examples of the material of the metal ion-containing cellulose fiber include wood fibers and non-wood pulp cellulose fibers, and regenerated cellulosic fibers. As the regenerated cellulosic fiber, rayon, cotton and cupra are specifically mentioned.
The metal ion-containing cellulose fiber can be obtained by bringing a metal compound aqueous solution into contact with an oxidized cellulose fiber having a carboxyl group or a carboxylate group introduced into the surface of the cellulose fiber. In addition, as a method for producing the base paper, in addition to a method in which the metal compound aqueous solution is brought into contact with a sheet formed from a raw material containing oxidized cellulose fibers, the metal oxide is previously contained in the oxidized cellulose fibers. Examples of the method for making a raw material containing the same can be given.

The oxidized cellulose fibers can be produced by oxidizing cellulose fibers such as wood pulp using an N-oxyl compound as a catalyst. By this oxidation reaction, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized, and oxidized cellulose fibers having a carboxyl group or a carboxylate group on the surface are obtained. The raw material cellulose is preferably natural cellulose. The above oxidation reaction is preferably performed in water. The concentration of the cellulose fiber in the reaction is not particularly limited, but is preferably 5% by mass or less. The amount of the N-oxyl compound may be about 0.1 to 4 mmol / L with respect to the reaction system. A known co-oxidizing agent may be used for the reaction. Examples of the co-oxidizing agent include dihalous acid or a salt thereof. The amount of the co-oxidizing agent is preferably 1 to 40 mol per 1 mol of the N-oxyl compound.
The reaction temperature is preferably from 4 to 40C, more preferably room temperature. The pH of the reaction system is preferably from 8 to 11. The degree of oxidation can be appropriately adjusted depending on the reaction time, the amount of the N-oxyl compound, and the like.
The oxidized cellulose fiber thus obtained has acid groups on the surface and hardly any acid groups inside. This is presumably because the cellulose fibers are crystalline and the oxidizing agent is not easily diffused into the fibers.

The carboxyl group refers to a group represented by -COOH, and the carboxylate group refers to a group represented by -COO-. The counter ion of the carboxylate group in producing the oxidized cellulose fiber is not particularly limited. Then, a metal ion described later replaces the counter ion and forms an ionic bond with the carboxylate group. The carboxyl group is considered to coordinate with the copper ion as a metal ion. A carboxyl group or a carboxylate group is also referred to as an “acid group”.
The content of the acid group can be measured by the method disclosed in paragraph 0021 of JP-A-2008-001728. That is, 60 mL of a 0.5 to 1% by mass slurry is prepared using a precisely weighed dry cellulose sample, and the pH is adjusted to about 2.5 with a 0.1 mol / L hydrochloric acid aqueous solution. Thereafter, a 0.05 mol / L aqueous solution of sodium hydroxide is dropped to measure the electric conductivity. The measurement is continued until the pH is about 11. From the amount (V) of sodium hydroxide consumed until the change in the electrical conductivity indicates a gradual neutralization step of the weak acid, the acid group amount X1 is determined using the following equation.
X1 (mmol / g) = V (mL) × 0.05 / mass of cellulose (g)

  The amount of the acid groups in the cellulose fibers is preferably from 0.2 to 2.2 mmol / g. When the amount of the acid group is less than 0.2 mmol / g, the amount of metal ions present on the surface of the cellulose fiber is not sufficient, and the deodorizing function may be poor. If the amount of the acid group exceeds 2.2 mmol / g, drainage during papermaking may be deteriorated and dehydration load may be increased.

Next, an aqueous solution containing the compound of the metal is brought into contact with the oxidized cellulose fiber, and a metal ion derived from the metal compound forms an ionic bond with a carboxylate group. The carboxyl group is considered to be ionized and ionically bonded to the metal ion via the carboxylate group, or coordinated with the metal ion as described above.
The aqueous metal compound solution is an aqueous solution of a metal salt. Examples of metal salts include complexes (complex ions), halides, nitrates, sulfates, and acetates. Preferably, the metal salt is water-soluble.
Regarding the contact method of the metal compound, a dispersion of cellulose fibers prepared in advance and an aqueous solution of the metal compound may be mixed, and a dispersion containing the cellulose fibers is coated on a substrate to form a film, and the metal compound is applied to the film. An aqueous solution may be added for impregnation. At this time, the film may be fixed on the substrate or may be separated from the substrate.
The concentration of the aqueous metal compound solution is not particularly limited, but is preferably from 10 to 80 parts by mass, more preferably from 30 to 60 parts by mass, per 100 parts by mass of the cellulose fibers.
The time for contacting the metal compound may be appropriately adjusted. The temperature at the time of contact is not particularly limited, but is preferably 20 to 40 ° C. The pH of the solution at the time of contact is not particularly limited, but if the pH is low, metal ions are less likely to be bonded to the carboxyl group.

The fact that the oxidized cellulose fiber contains (coordinates) metal ions can be confirmed by a scanning electron microscope image and ICP emission analysis of the extract with a strong acid. That is, the presence of metal ions cannot be confirmed in the scanning electron microscope image, while the presence of the metal can be confirmed in ICP emission analysis. On the other hand, for example, when the metal is reduced from ions and exists as metal particles, the metal particles can be confirmed in a scanning electron microscope image or a transmission electron microscope image. Can be determined. The presence or absence of metal ions can also be determined by scanning electron microscope images and element mapping. That is, although the metal ions cannot be confirmed in the scanning electron microscope image, the presence of the metal ions can be confirmed by performing element mapping.
By using an ion of the above metal element as a metal ion, an antibacterial function is provided. On the other hand, the metal particles do not have to be bonded to all of the acid groups of the cellulose fiber, and the remaining acid groups can also neutralize odorous components such as ammonia, thereby exhibiting a deodorizing function.

In the metal ion-containing cellulose fiber, the content of the metal ion with respect to the oxidized cellulose fiber is preferably 10 to 60 mg / g.
When the content of the metal ion is less than 10 mg / g, the antibacterial / deodorant performance of the metal ion-containing cellulose fiber may be reduced.
Producing a metal ion content exceeding 60 mg / g leads to a decrease in the yield of metal ion-containing cellulose fibers, which may increase the cost.

The nonwoven fabric sheet according to the embodiment of the present invention can be suitably used for, for example, a filter, a sanitary material, a wiping material, and the like, but the use is not particularly limited.
The present invention is not limited to the above-described embodiments, but extends to various modifications and equivalents included in the spirit and scope of the present invention.

  Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

<Production of metal ion-containing cellulose fiber>
After dispersing 5.00 g of undried softwood bleached kraft pulp by dry weight, 39 mg of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and 514 mg of sodium bromide in 500 ml of water, A 15% by mass aqueous solution of sodium hypochlorite was added to 1 g of pulp (absolutely dried) so that the amount of sodium hypochlorite was 5.5 mmol, and the reaction was started. During the reaction, the pH was kept at 10.0 by dropwise addition of a 3M aqueous solution of NaOH. The reaction was considered complete when the pH no longer changed, and after filtering the reaction product through a glass filter, washing with a sufficient amount of water and filtration were repeated twice to impregnate water with a solid content of 15% by mass. A TEMPO oxidized cellulose fiber was obtained.
This TEMPO oxidized cellulose fiber has a carboxyl group or a carboxylate group on its surface. Table 1 shows the acid group content (per 1 g of oxidized cellulose fiber) of the TEMPO oxidized cellulose fiber before containing metal ions.

This TEMPO oxidized cellulose fiber is an unbeaten cellulose nanofiber.
Next, a metal salt aqueous solution having a pH and a concentration (per 1 g of TEMPO oxidized cellulose fiber) shown in Table 1 was added to the obtained TEMPO oxidized cellulose fiber (containing no metal ions at this time), followed by stirring. As a result, metal ions were supported on the TEMPO oxidized cellulose fiber.
FIG. 1 shows a transmission electron microscope image of the metal ion-containing cellulose fiber used in the examples.

<Manufacture of nonwoven sheet>
Next, a metal ion-containing cellulose fiber and pulp were prepared.
Then, a stock was prepared by mixing the metal ion-containing cellulose fiber and the pulp at a compounding ratio shown in Table 2, and then a first web having a basis weight shown in Table 2 was formed by a wet papermaking method.
Further, a second web having a basis weight shown in Table 2 was directly formed from a raw material resin of polypropylene by a spun bond method.
Next, the first web and the second web were laminated, and the fibers of each web were bonded by a hydroentanglement method to produce a nonwoven fabric sheet.
As Comparative Example 1, a nonwoven fabric sheet was produced without mixing metal ion-containing cellulose fibers.

  In addition, in each example, ICP ((high frequency inductively coupled plasma) emission spectroscopy) of the extract after dissolving with a strong acid was performed, and it was confirmed that all of the extracts contained a metal. In the example, it is understood that the oxidized cellulose fiber contains metal ions.

The following evaluation was performed about the obtained nonwoven fabric sheet.
<Deodorant>
A nonwoven sheet sample of 10 cm × 10 cm was placed in a gas bag, and the deodorizing ability after injecting 0.5 L of 5 ppm hydrogen sulfide gas was sensory evaluated. As a comparison, a blank test was conducted in which a nonwoven fabric sheet sample was not installed in a gas bag. If the evaluation is ◎ or ○, there is no practical problem.
◎: No odor at all ○: Almost no odor ×: Odor equivalent to blank remains <antibacterial property>
Antibacterial test method and antibacterial effect of textile products Evaluated according to JIS-L1902: 2008 quantitative test (bacterial solution absorption method). There is no problem if the numerical value (bacteriostatic activity value) is 2.0 or more.

  Tables 1 and 2 show the obtained results.

As is clear from Table 2, each of the examples had sufficient deodorizing and antibacterial functions, and also had excellent strength.
On the other hand, in the case of Comparative Example 1 in which the content of metal ions with respect to the nonwoven fabric sheet was less than 60 mg / m ² , the deodorizing and antibacterial functions were significantly inferior to those of the examples.
In the case of Comparative Example 2 in which the nonwoven fabric sheet did not contain the metal ion-containing cellulose fiber, the deodorizing and antibacterial functions were significantly inferior to those of the examples.

Claims (3)

Ions of one or more metal elements selected from the group consisting of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn and Cu with respect to oxidized cellulose fibers having a carboxyl group or a carboxylate group on the surface. A nonwoven fabric sheet comprising a combination of a metal ion-containing cellulose fiber containing a synthetic fiber and at least one kind of fiber selected from the group consisting of polyethylene, polypropylene, and polyethylene terephthalate . The nonwoven fabric sheet according to claim 1, comprising 2 to 30% by mass of the metal ion-containing cellulose fiber . The nonwoven fabric sheet according to claim 1 , wherein the content of the metal ions in the nonwoven fabric sheet is 60 to 510 mg / m ² .